In the prior art, ski boots immobilized the foot and ankle of the skier, and the skier turned by swinging his knees and torso so that weight was applied over the edge of the skis in the direction of the turn. The background relating to these prior art boots and the drawbacks pertaining thereto are fully set forth in Eisenberg U.S. Pat. Nos. 4,074,446 and 4,144,659.
The above-identified patents disclose a means for turning by using the natural lateral tilting motion of the foot called inversion and eversion. This lateral tilting is a function of the sub talar joint of the ankle and foot, and by using this motion to tilt the ski boot-mounted insert of these inventions, the skier's weight can be transmitted to the edge of the ski without the need for swinging the knees and twisting the torso. Some skiers, however, because of tarsal coalitions, triple anthrodesis, calcaneal or talar fractures, inadequate peroneal musculature or other factors do not have the requisite sub talar motion and, therefore, are unable to invert or evert the foot as required.